Interference Management Based On Resource Allocation In Macro-Femtocell Networks

Offloading from macrocell and improving coverage can be realized from deployment of femtocells in the indoor scenario. The characteristic of femtocell is easy installation, automatic configuration, automatic network design, and plug-and-play. Femtocell is designed for improving the network capacity indoor and accessing to the internet by the wired backhaul. However, installing femtocells in these scenarios will lead to challenges:(1) Coexistence of multiple femtocells will produce co-tier interference to the users in the neighbouring cells. (2) In the coverage area of femtocells, the downlink interference signal will interfere the unauthorized macrocell users. (3) Because of the complex situations of the interference, the uniform interference management measure can not be utilized in different scenarios. Therefore, according to the up-to-date study worldwide, this dissertation focuses on the mentioned three challenges.First of all, for the complex interference in the two-tier network, the interference area partitioning method is considered, which can simplify the interference management strageties and provide the theoretical guidance for the practical project. The simulation results have verified that the co-tier-dominated, the cross-tier-dominated and the balanced area often coexist in the network;Secondly, for the application scenario in which the femtocell gateway is utilized to manage the resource uniformly, the centralized interference management schemes are studied. The centralized dynamic resource allocation algorithm is improved, while the traditional algorithms only discuss the PRB allocation. Therefore, the access failure rate will increase and the PRB efficiency will decrease along with the femtocell number. In order to improve the PRB efficiency, the user type is analyzed by the new algorithm, and the interference relationship is decided from the perspective of users. The energy efficiency resource allocation algorithm is proposed on the basis of dynamic resource allocation algorithm for reducing the energy consumption. The access criterion for the traditional femtocell network is the RSS (Received Signal Strength), but all the base stations should be active. The new algorithm in the dissertation can take off a portion of femtocell to realize the coverage. Then the theoretical analysis and simulation are worked out for the new algorithms, the average data rate, PRB efficiency, and energy efficiency are improved and the access failure rate is lower than the existing algorithms;Thirdly, when resource cannot be managed by the femtocell gateway and the network type is different, the semi-distributed interference management schemes are discussed. The data rate standard deviation is investigated to divide the network into biased and unbiased. The semi-distributed scheme is composed of two branches, which are applied to biased and unbiased network. The clustering factor for unbiased network is different from the biased network, and the traditional methods are appropriate to the unbiased network. So the novel clustering algorithm in the biased network is present to allocate the resource effectively. To the semi-distributed scheme, the resource is assigned uniformly in the clusters by the cluster header, but allocated parallelly among the clusters. We refer to the optimum results, and propose the subchannel and power allocation algorithms for the two kinds of network. The simulation results indicate that the fairness performance and subchannel allocation success rate can be promoted by the new algorithms;Finally, when all the femtocells are independent and the resource allocation cannot be operated by the femtocell gateway or the cluster header, we discuss the distributed interference management schemes. For the target of femtocell transmission power minimization, the Q-Learning interference management algorithm is present, which includes coordinated and autonomous algorithm. In the coordinated mode, the users can interact with the neighbouring femtocell users. In order to satisfy the users and disperse the impact of the interference, they can be classified by the fuzzy logic theory, and the orthogonal resource is assigned to the cell-edge ones with high data rate requirements. The resource is allocated directly with the power minimization criterion by the autonomous algorithm in the femtocell. On one side, cell-edge users with high data rate are satisfied by the algorithms as far as possible; On the other side, the co-tier interference to other users has been reduced. After that, the theoretic analysis and simulation are conducted respectively which has verified that the average data rate and energy efficiency performance are enhanced.